(1) Field of the Invention
The invention described herein is directed to a method and system for controlling the operation of a blood pump, for example controlling the flow or output of an implantable blood pump that is connected to a patient's circulatory system.
(2) Description of Related Art
U.S. Pat. No. 5,888,242 is directed to an automatic speed control system that continually adjusts the speed of an implanted cardiac assist blood pump to an appropriate level for the varying physiological needs of the patient. It does this by iteratively incrementing the speed setpoint of the pump. When the system detects the imminence of a ventricular collapse at diastole, it decrements the speed setpoint by a predetermined safety margin. An alarm condition is indicated if the setpoint decrease results in an insufficient blood flow rate through the pump. The flow rate and imminence of ventricular collapse are computed in real time as functions of the pump's motor current and speed setpoint.
International Publication No. WO 01/72352 A2 discloses a control system for rotodynamic blood pumps. A left ventricular assist device (LVAD) including a rotodynamic blood pump is powered by a brushless DC motor. Three feedback channels, one for each of voltage, current, and motor speed, provide inputs to a microcontroller or microprocessor. The three feedback waveforms are analyzed, and from these waveforms, motor input power, patient heart rate, current pump flow rate, and systemic pressure are determined. The microprocessor calculates a desired flow rate proportional to the patient heart rate, and communicates a new power output to a commutation circuit, which regulates power to the motor. The pump also includes safety checks that are prioritized over desired pump flow. These include prevention of ventricular suction, low pulsatility, minimum and maximum pump speed, minimum speed-relative pump flow, minimum absolute pump flow, minimum and maximum motor input power.